Summary of Work: Pneumocystis carinii is a major pathogen of patients with HIV infection. The immune responses to P. carinii are poorly understood, but cytokines may clay a role both in clearing P. carinii infection and in the hypoxia associated with P. carinii pneumonia (PCP) that may be exacerbated following initiation of therapy. Collaborative studies with investigators at Indiana University continue. Based on preliminary polymerase chain reaction studies, investigators at Indiana University are currently examining the potential role of IL-10 in the pathogenesis of PCP using a CD4 depleted mouse model. In addition, we have completed a study with Dr. Vogel examining the effects of IL-12 in scid mice with PCP. In this model no effect on PCP was seen when IL-12 was administered either at the time of exposure to P. carinii or 4 weeks after exposure. In the future, we plan to use the scid mouse model to further evaluate the role of individual cytokines in modulating P. carinii infection. It is hoped that these studies will provide insights into the role of cytokines in PCP, and may provide mechanisms for increasing clearance or decreasing the inflammation that may be causing hypoxia.